On the normal exponential map in singular conformal metrics

Brake orbits and homoclinics of autonomous dynamical systems correspond, via Maupertuis principle, to geodesics in Riemannian manifolds endowed with a metric which is singular on the boundary (Jacobi metric). Motivated by the classical, yet still intriguing in many aspects, problem of establishing multiplicity results for brake orbits and homoclinics, as done in [6, 7, 10], and by the development of a Morse theory in [8] for geodesics in such kind of metric, in this paper we study the related normal exponential map from a global perspective.Comment: 10 page

Morse Theory for geodesics in singular conformal metrics

Motivated by the use of degenerate Jacobi metrics for the study of brake orbits and homoclinics, we develop a Morse theory for geodesics in conformal metrics having conformal factors vanishing on a regular hypersurface of a Riemannian manifold.Comment: 22 pages. To appear in Communications in Analysis and Geometr

Functions on the sphere with critical points in pairs and orthogonal geodesic chords

Using an estimate on the number of critical points for a Morse-even function on the sphere $\mathbb S^m$, $m\ge1$, we prove a multiplicity result for orthogonal geodesic chords in Riemannian manifolds with boundary that are diffeomorphic to Euclidean balls. This yields also a multiplicity result for brake orbits in a potential well.Comment: 12 pages, 3 figure

Optimal Inflation Targeting Rules

This paper characterizes optimal monetary policy for a range of alternative economic models in terms of a flexible inflation targeting rule, with a target criterion that depends on the model specification. It shows which forecast horizons should matter, and which variables besides inflation should be taken into account, for each specification. The likely quantitative significance of the various factors considered in the general discussion is then assessed by estimating a small, structural model of the U.S. monetary transmission mechanism with explicit optimizing foundations. An optimal policy rule is computed for the estimated model, and shown to correspond to a multi-stage inflation-forecast targeting procedure. The degree to which actual U.S. policy over the past two decades has conformed to the optimal target criteria is then considered.

Nuclear Periphery in Mean-Field Models

The halo factor is one of the experimental data which describes a distribution of neutrons in nuclear periphery. In the presented paper we use Skyrme-Hartree (SH) and the Relativistic Mean Field (RMF) models and we calculate the neutron excess factor $\Delta_B$ defined in the paper which differs slightly from halo factor $f_{\rm exp}$. The results of the calculations are compared to the measured data.Comment: Proceedings of the Xth Nuclear Physics Workshop, Maria and Pierre Curie, Kazimierz Dolny, Poland, Sept 24-28, 2003; LaTex, 4 pages, 3 figure

Has Monetary Policy Become More Effective?

Recent research provides evidence of important changes in the U.S. economic environment over the last 40 years. This appears to be associated with an alteration of the monetary transmission mechanism. In this paper we investigate the implications for the evolution of monetary policy effectiveness. Using an identified VAR over the pre- and post-1980 periods we first provide evidence of a reduction in the effect of monetary policy shocks in the latter period. We then present and estimate a fully specified model that replicates well the dynamic response of output, inflation, and the federal funds rate to monetary policy shocks in both periods. Using the estimated structural model, we perform counterfactual experiments to determine the source of the observed change in the monetary transmission mechanism, as well as in the economy's response to supply and demand shocks. The main finding is that monetary policy has been more stabilizing in the recent past, as a result of both the way it has responded to shocks, but also by ruling out non-fundamental fluctuations.

Optimal Interest-Rate Rules: II. Applications

In this paper we calculate robustly optimal monetary policy rules for several variants of a simple optimizing model of the monetary transmission mechanism with sticky prices and/or wages. We discuss representations of optimal policy both in terms of interest-rate feedback rules that generalize the well-known Taylor rule,' and in terms of commitment to a target criterion of the kind discussed in familiar proposals for flexible inflation targeting.' Optimal rules, however, require that policy be history-dependent in ways not contemplated by many well-known proposals. We furthermore find that a robustly optimal policy rule is almost inevitably an implicit rule, that requires the central bank to use a structural model to project the economy's evolution under the contemplated policy action. Finally, our numerical examples suggest that optimal rules do not place nearly as much weight on projections of inflation or output many quarters in the future as occurs under the current practice of inflation-forecast targeting central banks.

Sticky prices and monetary policy : evidence from disaggregated U.S. data

This paper uses factor-augmented vector autoregressions (FAVAR) estimated using a large data set to disentangle fluctuations in disaggregated consumer and producer prices which are due to macroeconomic factors from those due to sectorial conditions. This allows us to provide consistent estimates of the effects of US monetary policy on disaggregated prices. While sectorial prices respond quickly to sector-specific shocks, we find that for a large number of price series, there is a significant delay in the response of prices to monetary policy shocks. In addition, price responses display little evidence of a “price puzzle,” contrary to existing studies based on traditional VARs. The observed dispersion in the reaction of producer prices is relatively well explained by the degree of market power, as predicted by models with monopolistic competition. JEL Classification: E32, E5